2.0 Analysis 2.1 Towing Systems Because the critical characteristic of a towing wire is its breaking strength in relation to the forces which it will experience in service, the TERRA NOVA SEA used a tow-line comparable in size and type to that adopted by the Canadian towing industry. Although a tow-line of considerable length was payed out on the first towing attempt, it did not absorb the shock created by the heavy seas. The use of heavy equipment on the third attempt proved successful. The anchor cable which was used as a chain bridle sagged under its own weight and provided a catenary (buffer) to absorb the relative motion between the tug and the towed vessel in the rough sea. Because the bridle legs were not reeved through side fairleads but through the forward centre fairlead, there was a reduction in the directional control of the vessel being towed and an increase in towing resistance. 2.2 Marine Diesel Oil Quality Analysis of the densities of the MDO and the HFO taken at Singapore and of the densities of the fuel in the vessel's tanks at Sept-les would suggest that the vessel's fuel was a mixture of MDO and HFO. The TSB laboratory test results (see Appendix D) show a viscosity at 40C of 65.2 in No. 37 settling tank, of 61.9 in No. 39 day tank, and of 80.9 in the header tank. The barge MDO sample indicated a viscosity of 6.81 at 40C. A further indication that the MDO and HFO were mixed is that the MDO delivered by the barge had 0.02% water and sediments and an ash content of 0.003% by mass. Tests indicate that tanks Nos. 37 and 39 and the header tank had much higher levels. Given the nature of the ash, it is likely that this contamination was introduced by mixing HFO with MDO. It could also have been caused by the condition of the vessel's fuel tanks. The high concentration of water and sediment in the header tank and the continuing dirty generator filter problem would also suggest that the purifier had not been used for some time, or that the purifier had been bypassed. 2.3 Marine Diesel Oil--Quantity and Consumption Although the records of the vessel's daily consumption of MDO may at first seem contradictory and irreconcilable, it appears that the vessel's true daily consumption was between 3.16 and 3.18 tonnes (see section 1.14). At this daily rate, the vessel had consumed more than the total quantity of MDO aboard since leaving Singapore. Even if allowance is made for amounts traditionally up the chief engineer's sleeve, it is scarcely possible that these would account for the 19 tonnes, approximately, which remained on board on arrival at Sept-les. As is also apparent from scientific testing of the fuel, at least some of the fuel remaining on board at Sept-les was obtained by mixing fuels. 2.4 Fuel and Generator Engine Problems Because the vessel had very little MDO fuel remaining at the time of the occurrence and had had a rough crossing of the Atlantic, it is possible that the proportion of sediment in suspension in the fuel tanks was higher than usual. The most likely origin of the sediment was fuel contamination resulting from the practice of mixing fuels. The problems which led to the breakdown of the generator prime movers were not new: the generator service records revealed a history of fuel contamination, choked fuel filters, malfunctioning fuel injectors, and heavy wear of cylinder liners and piston rings. 3.0 Conclusions 3.1 Findings Samples of the marine diesel oil (MDO) analyzed by the TSB Engineering Laboratory indicate that the fuel supplied in Singapore was within the specifications for the SKL diesel engines. The fuel in the day, settling, and header tanks at the time of the occurrence was not within the specifications required for the SKL engines, nor was it comparable to the MDO supplied in Singapore. The fuel in the header tank was found to be contaminated with water and sediments. The two SKL generators were found to be in very poor condition when opened up by the engine manufacturer's representative. A Port State Control inspection of the vessel uncovered numerous deficiencies with the vessel and the life-saving equipment on board. Under very severe weather conditions and in close proximity to land, the crew of the tug TERRA NOVA SEA was able to take the disabled PAL WIND in tow and avert what otherwise might have been a more serious occurrence. The tow-line used by the tug was comparable in size and type to that adopted by the Canadian towing industry. The initial tow-line did not absorb the shock created by the heavy seas. 3.2 Causes The PAL WIND became disabled because the fuel used for the generators did not comply with the manufacturer's specifications. The sub-standard condition of generators Nos. 1 and 2 also contributed to this occurrence. The Board has no marine safety recommendations to issue at this time.4.0 Safety Action The Board has no marine safety recommendations to issue at this time.